The present invention relates to a mechanical structure and a sliding member for mounting on the mechanical structure. More particularly, the present invention relates to a mechanical structure constructed from components that include one or more extrusions and a linear bearing assembly for slidably mounting to extrusions utilized in constructing the mechanical structure.
Modular construction of mechanical structures that include one or more extrusions as components is known. These extrusions may be constructed from material such as aluminum or an aluminum alloy. Aluminum or aluminum alloy has the advantage of allowing for the use of a lighter weight material in a mechanical design. Aluminum weighs only about one-third as much as materials such as iron, steel, copper, or brass from which many mechanical structures are constructed. At least one advantage of the use of such lightweight materials is reduced shipping and handling costs. In addition, aluminum has a higher strength-to-weight ratio than materials such as copper, carbon steel (A36), and stainless steel. The strength-to-weight ratio is a material's ultimate tensile strength divided by its density. The combination strength and light weight of aluminum have resulted in its widespread use in industries such as aerospace, machine building, and transportation.
Extrusions allow for modular construction of a variety of mechanical structures. These extrusions can be interconnected by various plates, fasteners, and studs such that welding for interconnection, as required with some conventional metals such as steel, is not required. Because welding is not required, heat stress and warpage of the components used to construct a mechanical structure is not a problem. In addition, elimination of welding makes construction of mechanical structures less expensive and less time consuming. Furthermore, elimination of welding and use of plates, fasteners, and studs for interconnection of extrusions results in mechanical structures that can be easily disassembled, with the extrusions thereof reused to construct additional mechanical structures.
Use of linear bearing assemblies is known. These bearing assemblies provide a means for integrating guided linear motion along at least a portion of a mechanical structure. Linear bearing assemblies are slidably mounted on a guide rail such that they are movable along at least a portion of the longitudinal length of the guide rail. Wear pads or other friction reducing structures having a low coefficient of friction are often disposed between the linear bearing and the guide rail.
A current mechanical structure constructed at least in part from one or more extrusions in which it was desired to integrate guided linear motion along at least a portion of an extrusion of the mechanical structure would require the attachment of a guide rail to the extrusion. This attachment would require utilization of such means as screws, bolts, rivets, or welding. Thus, many of the above-described advantages associated with modular construction of mechanical structures via the utilization of extrusions would be eliminated. A linear bearing assembly for releasably mounting directly to an extrusion of a mechanical structure would be a welcome improvement. As long as the linear bearing assembly could be removed from the extrusion without partial or complete destruction thereof, the above-described advantages associated with both the use of extrusions in the construction of mechanical structures and linear bearing assemblies therein would be maintained.
Accordingly, a mechanical structure is provided that includes a frame having at least one extrusion that has a predetermined longitudinal length and a cross-section that includes at least one guide groove. The guide groove may include a T-slot formed in the extrusion. The mechanical structure also includes a sliding member mounted directly on the extrusion for integrating guided linear motion along at least a portion of the mechanical structure. Structure for reducing wear between the sliding member and the extrusion is provided. The reducing wear structure is connected to the sliding member and has a portion adapted to be received within the guide groove of the extrusion. The portion of the reducing wear structure that is received in the guide groove of the extrusion may include an alignment key. In a preferred embodiment, the extrusion and sliding member are formed from either aluminum or an aluminum alloy. A preferred aluminum alloy is 6105-T5 aluminum alloy. Also in a preferred embodiment, the reducing wear structure is constructed from a material having a low coefficient of friction (i.e., a high lubricity). This material may be an ultra high molecular weight polyethylene.
In a preferred embodiment, the sliding member includes a guide block and the reducing wear structure includes a wear pad having a first wear surface for contacting an adjacent surface of the extrusion. The wear pad also has an alignment key adapted to be received within the T-slot of the extrusion. In this preferred embodiment, the frame may be modular. The frame may also have at least two extrusions and structure for connecting the extrusions together. The guide block may be substantially U-shaped in cross-section. The preferred embodiment also includes attaching structure for attaching the wear pad to the guide block. The attaching structure may releasably attach the wear pad to the guide block. The attaching structure may include at least one fastener that is received in an opening formed in the guide block and a tapped threaded hole formed in the wear pad.
The alignment key may be integrally formed on the wear pad. The alignment key may be substantially rectangular in cross-section. Furthermore, the alignment key may also extend along the longitudinal length of the wear pad.
In one embodiment, there are three wear pads attached to three separate portions of a guide block. Each of the wear pads has a first wear surface for contacting an adjacent surface of the extrusion and an alignment key. Each alignment key is adapted to be received within a separate T-slot of the extrusion. In yet another embodiment, there are four wear pads attached to four separate portions of the guide block. In this embodiment, each wear pad has a first wear surface for contacting an adjacent surface of the extrusion and an alignment key. Each alignment key is adapted to be received within a separate T-slot of the extrusion.
The present invention provides a method of constructing a mechanical structure so as to integrate guided linear motion along at least a portion of the mechanical structure. The method includes assembling the static mechanical structure such that at least one aluminum extrusion is utilized in assembling the mechanical structure. The aluminum extrusion has a cross-section that includes at least one T-slot. The method further includes mounting at least one aluminum linear bearing directly on the extrusion such that the linear bearing is movable along at least a portion of a longitudinal length of the extrusion. The method additionally includes releasably mounting wear pads on the linear bearing such that the wear pads are disposed between at least those surfaces of the aluminum linear bearing and the aluminum extrusion that come in physical contact with one another. The method may further include forming the aluminum extrusion and the linear bearing from 6105-T5 aluminum alloy. The method may also further include forming the wear pads from a material having a low coefficient of friction (i.e., a high lubricity). The material utilized in forming the wear pads may be constructed from ultra high molecular weight polyethylene.
The above-described mechanical structure and method associated with assembling this mechanical structure has many advantages. One of those advantages includes that the mechanical structure can have sliding linear motion along at least one extrusion utilized in constructing the mechanical structure. This sliding linear motion is achieved through the use of a linear bearing assembly that mounts directly to the extrusion. No guide rail separately mounted to the extrusion is necessary for the linear bearing assembly. That is, the linear bearing assembly freely moves on the extrusion itself. Wear reducing structure, such as wear pads, are the only items disposed between the linear bearing and the extrusion. This wear reducing structure prolongs both the life of the linear bearing and the extrusion. The absence of a guide rail or similar structure disposed between an extrusion and a linear bearing has the advantage of reducing the components necessary to achieve linear motion along at least a portion of a mechanical structure. This reduction in the number of components has a cost savings benefit. A labor savings benefit is also achieved in that a guide rail does not have to be separately attached to an extrusion, via such means as welding, of a mechanical structure in order to achieve linear motion thereon.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.